There exist a variety of electronic devices that receive a signal in the form of an analog wave and then process the waveform signal to obtain a desired result. In particular, the devices may monitor the received waveform signals by recording the waveforms. An electrocardiograph, which monitors electrical signals produced by a beating heart, is an example of such a device. Another example is a device that monitors light waves transmitted in an optical fiber. Another example is a voltage monitor that monitors the power transmitted in a wire.
The devices also may monitor the received waveform signals by comparing the waveforms to defined waveforms and producing a desired result when an abnormal waveform is detected. For example, an implanted cardiac pacer produces the stimulating voltage pulse when it detects a heart arrythmia. A heart monitor alerts medical personnel in the same event.
A waveform signal monitor that does not function properly can cause serious consequences. An improperly functioning biological waveform signal monitor, such as an electrocardiograph, cardiac pacer or heart monitor, can be fatal. Therefore, devices have been developed to test and calibrate waveform signal monitors. These devices produce waveform signals that simulate signals that are expected to be monitored.
A typical waveform signal simulator device contains several digitized waveforms in non-volatile memory such as a ROM. Upon a request a digitized waveform is recalled from memory and processed through a digital/analog convertor. The resulting analog waveform signal then is sent to the monitor to be tested or calibrated. The monitor's response to a known waveform or series of waveforms then can be observed.
Present waveform signal simulators contain one or relatively few digitized waveforms in non-volatile memory. The digitized waveforms will vary according to the anticipated use of the simulator. For example, a simulator for use with a cardiac pacer or electrocardiograph may contain an R-wave and several common arrythmia waveforms. A simulator for use with an optical fiber transmission monitor may contain backscatter waveforms associated with several common imperfections in the fiber.
A simulator can be manufactured with a few digitized waveforms permanently placed in non-volatile memory. Such a simulator is greatly limited because it can only produce the few waveform signals that are defined when the simulator is manufactured. Alternatively, a simulator can be manufactured to receive a removable cartridge that contains a few digitized waveforms in non-volatile memory. Such a simulator is less limited because a theoretically infinite number of cartridges can be used with the simulator. However, the number of waveform signals that such a simulator can produce at any given time is limited by the number of cartridges the simulator can receive at one time and by the number of waveforms that can be placed in each cartridge.
Regardless of the method by which digitized waveforms are provided in a simulator, there remains the problem of defining the waveforms to be provided. As mentioned above, a waveform signal simulator typically is intended to be used with a particular type of monitor. Therefore, the common waveform signals expected to be detected by a particular monitor will be provided in the associated waveform signal simulator. However, there is no systemized method by which new, uncommon or non-existent waveforms are defined and provided to waveform signal simulators.
In the prior art, when the user of a waveform signal simulator desired to use an undefined waveform, the user would send a drawing of the waveform to the simulator manufacturer. The simulator manufacturer would digitized the waveform and place the digitized waveform in non-volatile memory. The simulator manufacturer then would send to the user a simulator or a cartridge that contained the digitized waveform in non-volatile memory.
In some cases, the simulator user may have defined the desired waveform with a series of data points representing amplitude along a time axis. In these cases the simulator manufacturer merely has to place the defined waveform into non-volatile memory.
The difficulty with prior art methods is that the simulator user must either accept only a few common waveforms provided with the simulator or be able to give to the simulator manufacturer a drawing or definition of a desired but previously undefined waveform. There exists a need for a system allowing the user to select from a large variety of possible waveforms in resident memory rather than independently developing those waveforms.